I. Field of the Invention
This disclosure relates generally to assaying and, more specifically, to methods and apparatus for assaying an analyte.
II. Description of Related Art
Different types of biosensors are known, along with their specific advantages and disadvantages. For example, electrochemical biosensors, surface acoustic wave sensors and surface plasmon resonance biosensors are known biosensors that have the advantage of not requiring the use of labeling techniques for most applications. However, these sensors also have certain disadvantages.
A current method for assaying an analyte (e.g., antibodies and/or antigens) in a fluid sample is accomplished using surface plasmon resonance (“SPR”) techniques. In such a technique, the presence of an analyte is determined by a change in the refractive index at a solid optical surface when the analyte interacts with a refractive index enhancing species, thereby causing binding or release of the species from the surface. In this respect, the SPR signal is a measure of mass concentration at a sensor chip surface. This means that the analyte/ligand association and dissociation in the sample can be observed and, ultimately, rate constants as well as equilibrium constants can be determined.
However, as was noted above, acquiring such SPR measurements has some disadvantages. In this respect, systems for carrying out such analyses are typically expensive as those systems generally employ a quartz prism as well as a radiation source that is capable of generating polarized light. Also, the response of an SPR sensor depends on the volume and refractive index of the bound analyte. Therefore, for very small molecules, this technique results in very small changes of refractive index and can make detecting such analytes difficult.
Another current approach for detecting an analyte is the use of an optical based sensing device for detecting the presence (and amount of) an analyte using both indicator and reference channels. The sensing device used in such an approach typically includes a sensor body with a radiation source contained therein. The radiation emitted by the source interacts with molecules in the material (i.e., the sample) being analyzed, which typically results in a change of at least one optical characteristic of those molecules. Such a change is not desirable as it may reduce the accuracy of information regarding the analyte obtained. Therefore, based on the foregoing, a need exists for improved methods and apparatus for assaying analytes.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.